Railroad locomotives such as diesel-electric locomotives transport goods and people on rails. Diesel-electric locomotives are powered by diesel engines that drive electric generators, which, in turn, drive electric motors that drive the locomotives' wheels. In various conventional diesel-electric locomotives, a diesel fuel tank is mounted to the locomotive between the front and rear wheels on an underside of the locomotive.
There has been increasing interest in using natural gas to power railroad locomotives, based on the relative price of natural gas and diesel fuel on a per unit of energy basis. Railroad locomotives have been designed to facilitate the use of a combination of diesel fuel and natural gas to drive the locomotive's engine(s) using the diesel cycle. Various conventional arrangements for dual fuel (e.g., natural gas and diesel fuel) configurations for locomotives call for a separate vehicle, also referred to as a fuel tender or a locomotive appurtenance, that contains the natural gas storage vessels in the form of liquid natural gas (LNG) or in the form of compressed natural gas (CNG) while the locomotive carries the conventional diesel fuel tank. The fuel tender connects to the locomotive to supply natural gas from the tender to the locomotive and its engine(s).
Marine vessels (e.g., large ships) are configured to combust multiple different fuels and will typically combust the cheapest fuel permitted in their location. More specifically, large ships typically combust heavy fuels (e.g., No. 6, which is also known as Bunker C, Furnace Fuel Oil, FFO, or Residual Fuel Oil) in unregulated zones (e.g., open sea). The large ships switch to cleaner fuels such as low sulfur diesel in regulated zones (e.g., near coastline).
To traverse through water, large ships include engines configured to burn the above fuels (these engines are referred to as diesel engines, although as stated above, the engines may be configured to burn, for example, Bunker C) that drive electric generators, which in turn, power the ship's propellers to push the ship through water. Conventional ships store the various fuels (e.g., Bunker C and low sulfur diesel) in separate vessels. In some cases, the engines of the large ships drive the propellers via a mechanical transmission and without use of intermediate electric generators.